During that time, the rates of Pseudomonas aeruginosa bacteria samples that were resistant to at least three types of antibiotics rose from about 15 percent to 26 percent, the investigators found.

Meanwhile, the rate of bacteria samples resistant to carbapenems -- a class of antibiotics considered one of the treatments of last resort for highly resistant infections -- rose from just over 9 percent to 20 percent.

Drug resistance was more common among children in intensive care units, those aged 13 to 17, and those in the Midwest, the findings showed.

The study offers more evidence of the need for aggressive strategies to track, prevent and treat antibiotic-resistant infections in children, the researchers said.

The findings were published Nov. 17 in the Journal of the Pediatric Infectious Diseases Society.

"Infections with P. aeruginosa can be serious," study author Dr. Latania Logan, from Rush University Medical Center in Chicago, said in a journal news release.

These infections can cause lengthy illness, longer hospital stays and increased risk of death in children, she added.

Another study author, Dr. Sumanth Gandra from the Center for Disease Dynamics, Economics & Policy, in Washington, D.C., said, "Highly drug-resistant P. aeruginosa infections leave health care providers with limited -- or sometimes no -- antibiotic choices available, and these antibiotics are less safe and more toxic in children."

Each year, there are about 51,000 health care-associated P. aeruginosa infections in adults and children in the United States, according to the U.S. Centers for Disease Control and Prevention. More than 6,000 of these infections are resistant to multiple classes of antibiotics, resulting in about 400 deaths annually.